This invention is related to co-pending U.S. application Ser. No. 07/347,260, filed on May 4, 1989 now U.S. Pat. No. 5,026,507, entitled "Fluorescent Whitening Agents, Products Comprising the Agent and Method of Use Thereof", U.S. application Ser. No. 07/347,328, filed on May 4, 1989 now U.S. Pat. No. 4,954,566, entitled "Preparation of Polymers with Pendant Organic Moieties Bound thereto via Ester and/or Amide Bridges", U.S. application Ser. No. 07/426,866 filed on Oct. 26, 1989 now abandoned, entitled "Cellulosic Pulp of High Brightness and Retention Characteristics and Methods of Preparation Thereof", U.S. application Ser. No. 07/401,624 filed on Aug. 31, 1989 now U.S. Pat. No. 4,963,625, entitled "Polyacrylamide Whitener of High Brightness and Retention and Low Toxicity and Method of Increasing Paper Whiteness" and U.S. application Ser. No. 07/401,427 filed on Aug. 31, 1989 now U.S. Pat. No. 5,043,370, entitled "Polyalkylene Imide of High Brightness and Retention Characteristics and Low Toxicity and Method of Increasing Paper Whiteness", all by the present inventors and assignors.
This invention relates to quaternary ammonium fluorescent compounds, products comprising them, a method for preparing the compounds, and to their use as whitening agents, particularly in coating formulations to increase the whiteness of paper products. The present agents evidence low biological toxicity as well as high whitening characteristics and are therefore particularly suited for packaging food products.
The brightness of bleached paper products can be increased by adding fillers such as titanium dioxide and fluorescent whitening agents to the paper or coating the paper with such products However, the use of fluorescent whitening agents is usually more economical, and is therefore progressively becoming more common than the use of titanium dioxide.
On the other hand, the use of known fluorescent whitening agents is not free from biological and environmental consequences. This becomes of particular importance when applied to the manufacture of paper products which are to be placed in contact with edibles such as foods and the like.
At the present time there are no known fluorescent whitening agents of low biological and environmental impact which are being used in the manufacture of paper products in the food industry in the United States.
Only one fluorescent whitening agent has, to the present time, been approved by the Food and Drug Administration (FDA) for use in food related applications. This agent is manufactured by Ciba-Geigy and sold as Uvitex OB. The product is highly insoluble in water and is marketed as a plastic additive (U.S. Pat. No. 4,642,322 to Wehner et al).
Anthranilic acid and various derivatives thereof have been known, as are known their low toxicity and high fluorescent characteristics.
U.S. Pat. No. 4,642,322 referred to above discloses the addition of anthranilic acid amide as a stabilizer to thermoplastics. Titanium dioxide is also utilized by this patent. However, the product is provided not as a coating formulation for use in paper products but as a thermoplastic for use in plastics.
Amino benzoic acids have been disclosed as being useful for the preparation of polybenzamide in the presence of U.S. Pat. No. 4,696,999 discloses such products as well as amino benzoic acid esters for use in the synthesis of polybenzamides. The amino benzoic acids and esters thereof described in this patent are, however, meta- and para-amino compounds, and are therefore positional isomers of the esters and acids of this invention. In addition, this patent proposes the use of these compounds to form pulps of short fiber materials with high stability values. This patent also discloses in Example A a condensation reaction of 4-aminobenzoic acids with titanium chloride but nowhere is there a disclosure of use of the compounds in paper products.
U.S. Pat. No. 4,481,186 to Speakman describes a copolymer pigment dispersant suitable for use in the preparation of paints and para-aminobenzoic acid is one of the components utilized. Another component is titanium dioxide which is used as a pigment for color. No mention of any utility in terms of the utilization of the products for coating paper is stated.
Aminobenzoic acid is also used in admixture with a coloring agent such as titanium dioxide for the preparation of cosmetic and skin treatment compositions in U.S. Pat. No. 4,481,186. The prior art cosmetic and skin treatment compositions are generally speaking coating formulations but they are not paper whitening coating compositions.
A condensate of para- or meta-aminobenzoic acid and titanium dioxide is disclosed in U.S. Pat. No. 4,607,703. These materials are incorporated into molding polyamide compositions but are not suggested for use in paper coatings.
Titanium dioxide is used as a pigment and 4-aminobenzoic acid as a compound capable of providing an activated ester group in the preparation of self cross-linking heat-curable grinding resins in U.S. Pat. No. 4,539,385. No mention of paper coatings in this patent can be found.
Fluorescent whitening agents work by emitting bluish light upon excitation in the long ultra violet region (about 350-400 nm). This light can compensate for the yellowness inherent to paper products.
For example, methyl anthranilate and methyl N-methyl anthranilate have been reported to be non-mutagenic in short-term microbial assays (Shimizu, H. and Takemura, N., "Mutagenicity of Some Aniline Derivatives", in Orford, R. R., Cowell, J. W., Jamieson, G. G., and Love, E. J., editors, "Occupational Health in the Chemical Industry", pp 497-506, MEDICHEM Calgary 1983 Association, Calgary (1983).
U.S. Pat. No. 4,501,767 discloses a method of forming a multicoat by using an accelerator which can be the reaction product of an ortho-, meta- or para-amino benzoic acid with a polymerizable unsaturated carboxylic acid or polymerizable unsaturated alcohol and an epoxy resin or polyepoxy compound. This prior art patent contains no suggestion of the epoxy component being a quaternary ammonium derivatized epoxide.
U.S. Pat. No. 3,968,085 discloses aromatic polyamine compositions useful as hardening agents. The polyamines may be prepared by using an aminobenzoic acid as a reactant. The polyamines of this prior art patent are also disclosed as being hardeners for epoxy resins. This patent does not mention any reaction with an anthranilic acid or ester thereof with a quaternarized epoxy resin.
Accordingly, there is still a need for a low toxicity inexpensive whitening agent suitable as a paper additive for use in packaging in the food industry.